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Solar Energy Part 1: Resource

Solar Energy Part 1: Resource. San Jose State University FX Rongère January 2009. Sun characteristics. Temperature: 5,780 K Diameter: 1.4 10 6 km Distance: 150 10 6 km. Black Body radiation intensity. Sun emission is close to the back body spectrum: Photon energy:

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Solar Energy Part 1: Resource

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  1. Solar EnergyPart 1: Resource San Jose State University FX Rongère January 2009

  2. Sun characteristics • Temperature: 5,780 K • Diameter: 1.4 106 km • Distance: 150 106 km

  3. Black Body radiation intensity • Sun emission is close to the back body spectrum: • Photon energy: • Planck’s spectral distribution of emissive power of a black body in a vacuum: iλ,b: Radiation intensity of the black body in function of the wave length (W.m-2.μm-1.sr-1) h: Planck’s constant: 6.626.10-34 J.s c: Light velocity 3. 108 m.s-1 k: Boltzmann’s constant: 1.381. 10-23 J.K-1 T: Black body temperature K λ: Wave length m

  4. Solar Radiation Visible Infrared

  5. Sun Radiation Power • The energy radiated by the sun is calculated by integrating the Planck’s function: σ: Stefan-Boltzmann constant 5.67. 10-8 W.m-2.K-4

  6. Radiation received by the earth • Distance effect 150 M km

  7. Radiation received by the earth • The flux received by square meter out of the atmosphere is:

  8. Absorption by the atmosphere 2 Solar Spectral Irradiance (103 W.m-2.μm-1) 1 H2O H2O & CO2 0 Wavelength (m)

  9. Computation of the flux received by a cell • The flux received by a cell depends on: • the angle of the sun rays with the cell • the absorption by the atmosphere • Angle calculations: Sun position in the earth coordinates Sun position in local coordinates Sun position in the cell coordinates Declination (δs) Hour-angle (ωs) Normal angle (θs) Altitude (γs) Azimuth (αs) Local Time (LT) Latitude (φ) Longitude (λ) Cell orientation (γc,αc) Universal Time (UT) Local Time (LT) Latitude (φ) Longitude (λ)

  10. Greenwich Sun position in earth coordinates • Two coordinates: • Declination (angle from the Equator) δs • Hour-angle (angle from the meridian of Greenwich) ωs

  11. Equation of time • Correction to the Hour-angle (ωs) due to the elliptical orbit of the earth around the sun

  12. Equation of time • Difference between local solar time and local mean solar time Woolf approximation

  13. Declination • Earth oscillates along its polar axis See: http://www.powerfromthesun.net/chapter3/Chapter3Word.htm

  14. αC γC Position of the sun in the sky • Two coordinates: • Azimuth (angle from the North) αs • Altitude (angle over the horizon) γs

  15. Absorption calculation • “A Simplified Clear Sky model for Direct and Diffuse Insulation on Horizontal Surfaces” R.E. Bird, R.L. Hulstrom SERI TR-642-761 February 1981 • Altitude • Barometric pressure (mb, sea level = 1013) • Ozone thickness of atmosphere (cm, typical 0.05 to 0.4 cm) • Water vapor thickness of atmosphere (cm, typical 0.01 to 6.5 cm) • Aerosol optical depth at 500 nm (typical 0.02 to 0.5) • Aerosol optical depth at 380 nm (typical 0.1 to 0.5) • Forward scattering of incoming radiation (typical 0.85) • Surface albedo (typical 0.2 for land, 0.25 for vegetation, 0.9 for snow) • Excel model to download at http://www.ecy.wa.gov/programs/eap/models.html Look for Solrad – Greg Pelletier

  16. Examples 37.3N – 121.8W 47.6N – 122.3W Energy for the day: 8.6 kWh/m2 Energy for the day: 8.9 kWh/m2 Power is in Watt [W] Energy is in Joule [J] or in [kWh]

  17. Parameter Influence • Each Parameter is valued to min and max: • Aerosols have the most influence followed by water vapor

  18. Radiation received by a panel • Radiation is equal to the radiation received by the projection of the panel to normal to the beam θ

  19. Cartesian Coordinates Cartesian coordinates of the opposite of the beam from the sun: z - Zenith φs y - East γs π-αs x - South

  20. Cartesian Coordinates Cartesian coordinates of the vector normal to the panel: z - Zenith γc y - East γs π-αc π-αs x - South

  21. Scalar product If Then the radiation is received by the back of the panel. The net radiation on the panel is null.

  22. Tracker vs Fix Panel • Summer

  23. Tracker vs Fix Panel • Spring A fix panel solar will provide about 30% less energy than a tracking system

  24. Direct and Diffuse Radiation • Direct and diffuse radiation

  25. Annual average of daily solar energy • Capacity Factor: • Example: • If Annual average of daily solar energy equals 6 kWh.m-2/day

  26. Map of solar radiation

  27. California Resources Source: California Solar Resources CEC-300-2005-007 April 2005

  28. Other sources • Energy Plus standard files for California climate zones (DOE) • http://www.eere.energy.gov/buildings/energyplus/cfm/weather_data3.cfm/region=4_north_and_central_america_wmo_region_4/country=2_california_climate_zones/cname=California%20Climate%20Zones • Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors (NREL) • http://rredc.nrel.gov/solar/pubs/redbook/ • NASA Surface meteorology and Solar Energy • http://eosweb.larc.nasa.gov/cgi-bin/sse/register.cgi

  29. Shading effect • Shading suppress direct flux • Diffuse flux is less than 20% of direct flux • In addition, energy level of most photons in diffuse radiation is too low to activate conductance for silicon output of shaded cells is almost zero • Cells of a solar panel are in series shade on few cells leads to almost null output

  30. Solar Path Finder Source: http://www.solarpathfinder.com/works.html?id=VQjGmAZv

  31. Solar Path Finder Results http://www.solarpathfinder.com/video?id=TwtmyFfS

  32. San Francisco Solar Map http://sf.solarmap.org/#

  33. San Francisco Solar Map

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